How to do same without Extension Method

Question

I have a program that displays output in XML format on console windows, that runs perfectly fine without any error, but I am using the Extension Method to do the job. How to do this without using the extension method, I Have a hint that I just need to move one piece of line from extension class to program class but as a new programmer I failed and need your help.

Here is my Main Class

List<int> email = new List<int>() { 60, 50, 70, 30, 80, 65, 90, 75, 55 };

        var element = new XElement("Results",
            email.Batch(3)
                 .Select(batch =>
                     new XElement("Result",
                                  batch.Select(mark => new XElement("Mark", mark)),
                                  new XElement("Total", batch.Sum()))));
        Console.WriteLine(element);



        Console.ReadLine();

Here is my Extension Method class

 public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> items,
                                                  int maxItems)
    {
        return items.Select((item, inx) => new { item, inx })
                    .GroupBy(x => x.inx / maxItems)
                    .Select(g => g.Select(x => x.item));
    }

Answer 1

If I understand correctly, you're asking how to move your extension code into your calling code. Here's how it would look like:

        List<int> email = new List<int>() { 60, 50, 70, 30, 80, 65, 90, 75, 55 };

        var element = new XElement("Results",
            email
                .Select((item, inx) => new { item, inx })
                .GroupBy(x => x.inx / 3)
                .Select(g => g.Select(x => x.item))                
                .Select(batch =>
                    new XElement("Result",
                        batch.Select(mark => new XElement("Mark", mark)),
                        new XElement("Total", batch.Sum())
                    )
                )
        );
        Console.WriteLine(element);
        Console.ReadLine();